not competed by kB or negative control competi- 
tors in molar excess. By UV crosslinking, protein 
complexes of ~160, —120, and ~95 kDa that inter- 
act with this site have been detected. DNA foot- 
printing suggests that this protein contacts DNA 
both within the IL-2R kB sequence and in the flank- 
ing region. 
Further evidence was recently obtained for the 
existence of such a protein by identifying a cDNA 
clone that binds specifically to the IL-2R kB se- 
quence. By Northern blot analysis, this clone hy- 
bridizes to a cellular mRNA ~5 kb in length. It is 
expressed in lymphoid cells and exists in a single 
copy in the genome. This gene differs from a pre- 
viously described cDNA that binds to the kB and 
H2TF1 sites, suggesting that there is heterogeneity 
among the genes and proteins that bind to KB-like 
sites. 
Dr. Nabel has begun to develop systems that uti- 
PUBLICATIONS 
lize viral vectors to express biologically active pro- 
teins in cells and tissues in vivo. A method to 
express recombinant genes within endothelial cells 
of the arterial wall of pigs, using a murine am- 
photropic transducing retroviral vector in endothe- 
lial cells, has been developed. Although P-ga- 
lactosidase was used for initial studies, other 
biologically active proteins, including angiogenic 
factors, growth factors, or transcription regulatory 
proteins, are being introduced. The goal of this re- 
search is to understand basic mechanisms of gene 
regulation and transcriptional activation and to de- 
fine the biological significance of factors that regu- 
late gene expression in complex organisms. 
Dr. Nabel is Assistant Professor of Internal Medi- 
cine and Biological Chemistry and a member of the 
Cell and Molecular Biology Department at the Uni- 
versity of Michigan Medical School. 
Articles 
Griffin, G.E., Leung, K., Folks, T.M., Kunkel, S., and Nabel, G.J. 1989. Activation of HIV gene expression dur- 
ing monocyte differentiation by induction of NF-kB. Nature 339:70-73. 
Nabel, E.G., Plautz, G., Boyce, F.M., Stanley, J.C., and Nabel, G.J. 1989. Recombinant gene expression in vivo 
within endothelial cells of the arterial wall. Science 244:1342-1344. 
Osborn, L., Kunkel, S., and Nabel, G.J. 1989. Tumor necrosis factor a and interleukin 1 stimulate the human 
immunodeficiency virus enhancer by activation of the nuclear factor kB. Proc Natl Acad Sci USA 86:2336- 
2340. 
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